U.S. patent application number 11/957039 was filed with the patent office on 2008-08-28 for delivery apparatus and methods for vertebrostenting.
Invention is credited to Martin Bruggemann, James Cannon, James Coyle, Liam Farrissey, Dion Gallagher, John V. Hamilton, John Mugan, Damien Ryan, Ronald Sahatjian, Andrew R. Sennett, Francisca Tan-Malecki.
Application Number | 20080208320 11/957039 |
Document ID | / |
Family ID | 39273094 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080208320 |
Kind Code |
A1 |
Tan-Malecki; Francisca ; et
al. |
August 28, 2008 |
Delivery Apparatus and Methods for Vertebrostenting
Abstract
The invention relates to a method of delivering and deploying a
stent into a curvilinear cavity within a vertebral body or other
bony or body structure. The invention also relates to devices that
may be used to perform the steps to deliver and deploy a stent.
Inventors: |
Tan-Malecki; Francisca;
(Waltham, MA) ; Hamilton; John V.; (Foxboro,
MA) ; Sennett; Andrew R.; (Hanover, MA) ;
Sahatjian; Ronald; (Lexington, MA) ; Coyle;
James; (Oranmore, IE) ; Cannon; James;
(Clarinbridge, IE) ; Farrissey; Liam; (Kingston,
IE) ; Mugan; John; (Moycullen, IE) ;
Bruggemann; Martin; (Chapelizod, IE) ; Gallagher;
Dion; (Newmarket of Fergus, IE) ; Ryan; Damien;
(Headford Road, Galway City, IE) |
Correspondence
Address: |
GOODWIN PROCTER LLP;PATENT ADMINISTRATOR
EXCHANGE PLACE
BOSTON
MA
02109-2881
US
|
Family ID: |
39273094 |
Appl. No.: |
11/957039 |
Filed: |
December 14, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60875173 |
Dec 15, 2006 |
|
|
|
60875114 |
Dec 15, 2006 |
|
|
|
Current U.S.
Class: |
623/1.17 ;
623/1.11; 623/1.53 |
Current CPC
Class: |
A61B 17/16 20130101;
A61B 17/1617 20130101; A61B 17/8805 20130101; A61B 17/1642
20130101; A61B 17/8822 20130101; A61B 17/1671 20130101; A61B 17/88
20130101; A61B 17/885 20130101; A61B 17/8816 20130101; A61B 17/1637
20130101; A61B 17/8808 20130101; A61B 17/8858 20130101 |
Class at
Publication: |
623/1.17 ;
623/1.11; 623/1.53 |
International
Class: |
A61F 2/06 20060101
A61F002/06 |
Claims
1. A method of deploying a stent within an enlarged curvilinear
void created in a bony structure, the method comprising the steps
of: inserting a distal end of a stent delivery system through a
cannula and into a curvilinear void created in a bony structure;
deploying a self-expanding cement-directing stent within the
curvilinear void, wherein the self-expanding stent is releasably
attached to the distal end of the stent delivery system; attaching
a cement injecting syringe to a proximal end of the stent delivery
system; injecting cement through the stent delivery system and into
the stent; terminating the cement injection when the volume of
cement injected exceeds an interior volume of the expanded stent;
and releasing the stent from the stent delivery system.
2. The method of claim 1, wherein the self-expanding
cement-directing stent comprises a multifilament braided, polymer
impregnated, self-expanding, cement-directing stent.
3. The method of claim 1, wherein the stent delivery system
comprises a handle and an elongate shaft, and wherein the stent is
releasably attached to a distal end of the elongate shaft.
4. The method of claim 3, wherein the stent is released by
actuating a user control mechanism on the handle.
5. The method of claim 3, wherein the elongate shaft comprises at
least one of an inner shaft, an outer shaft, a tubular sheath, a
flexible guidewire, and an internal polymer extrusion.
6. The method of claim 5, wherein prior to the deploying step the
self-expanding cement-directing stent is collapsed on a distal end
of at least one of the inner shaft, the guidewire, and the polymer
extrusion.
7. The method of claim 6, wherein the self-expanding
cement-directing stent is deployed by retracting at least one of
the inner shaft, the outer shaft, the flexible guidewire, and the
polymer extrusion.
8. The method of claim 5, wherein prior to the deploying step the
self-expanding cement-directing stent is restrained in a collapsed
condition by the tubular sheath.
9. The method of claim 8, wherein the self-expanding
cement-directing stent is deployed by slideably retracting the
tubular sheath to allow the stent to self-expand within the
enlarged curvilinear void.
10. The method of claim 1, wherein the deploying step comprises
actuating a rotating cam mechanism.
11. The method of claim 3, wherein the stent is further releasably
attached at a distal end thereof.
12. A stent delivery system for deploying a stent within an
enlarged curvilinear void created in a bony structure comprising: a
handle; an elongate shaft adapted to releasably hold a
self-expanding cement-directing stent at a distal end thereof,
wherein the elongate shaft comprises a sheath and at least one of
an inner and an outer shaft; and at least one user control
mechanism adapted to deploy the stent.
13. The system of claim 12, wherein the at least one user control
mechanism comprises a rotating cam mechanism.
14. The system of claim 13, wherein actuating the rotating cam
mechanism retracts the sheath towards the handle.
15. The system of claim 14, wherein actuating the rotating cam
mechanism simultaneously extends the distal end of at least one of
the inner and the outer shaft away from the handle.
16. The system of claim 12, wherein a distal end of the handle
comprises an interface element adapted to releasably engage at
least a portion of proximal end of a cannula.
17. The system of claim 12, further comprising a stent release
mechanism adapted to release the stent from the elongate shaft.
18. A user control mechanism for a stent delivery device,
comprising: a support element; at least one cam shaft helically
positioned on the support element; a linear support sleeve; and at
least one pin engaging the cam shaft and the linear support sleeve,
wherein the cam shaft and the linear support sleeve are adapted to
force the pin linearly along an axial extent of the user control
mechanism upon a rotation of the support element.
19. The user control mechanism of claim 18, wherein the at least
one pin is attached to an elongate shaft extending from a distal
end of the user control element.
20. The user control mechanism of claim 19, wherein the elongate
shaft comprises at least one of an inner shaft, an outer shaft, and
a sheath.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to U.S. patent application
Docket No. SOT-004, entitled "Devices and Methods for
Vertebrostenting," and filed of even date herewith, the disclosure
of which is being incorporated herein by reference in its entirety.
This application claims priority to and the benefit of U.S.
provisional patent application Ser. No. 60/875,114 filed Dec. 15,
2006, and U.S. provisional patent application Ser. No. 60/875,173
filed Dec. 15, 2006, the disclosures of which are being
incorporated herein by reference in their entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the field of
orthopedic devices to treat fractured bone in the spine, and more
particularly to an orthopedic instrument and implant system that
can be used to facilitate bone cement treatment of a vertebral
compression fracture.
BACKGROUND OF THE INVENTION
[0003] There are many disease states that cause bone defects in the
spinal column. For instance, osteoporosis and other metabolic bone
conditions weaken the bone structure and predispose the bone to
fracture. If not treated, certain fractures and bone defects of the
vertebral body may produce intolerable pain, and may lead to the
development of deformity and severe medical complications.
[0004] Bone weakening may also result from benign or malignant
lesions of the spinal column. Tumors often compromise the
structural integrity of the bone and thus require surgical
stabilization and repair of defects with biocompatible materials
such as bone grafts or cements. Bone tumors of the spine are
relatively common, and many cause vertebral compression
fracture.
[0005] More than 700,000 osteoporotic compression fractures of the
vertebrae occur each year in the United States--primarily in the
elderly female population. Until recently, treatment of such
fractures was limited to conservative, non-operative therapies such
as bed rest, bracing, and medications.
[0006] One surgical technique for treating vertebral compression
fracture can include injecting or filling the fracture bone or bone
defect with biocompatible bone cement. A relatively new procedure
known as "vertebroplasty" was developed in the mid 1980's to
address the inadequacy of conservative treatment for vertebral body
fracture. This procedure involves injecting radio-opaque bone
cement directly into a fracture void, through a minimally invasive
cannula or needle, under fluoroscopic control. The cement is
pressurized by a syringe or similar plunger mechanism, thus causing
the cement to fill the void and penetrate the interstices of a
broken trabecular bone. Once cured, the cement stabilizes the
fracture and eliminates or reduces pain. Bone cements are generally
formulations of non-resorbable biocompatible polymers such as PMMA
(polymethylmethacrylate), or resorbable calcium phosphate cements
which allow for the gradual replacement of the cement with living
bone. Both types of bone cements have been used successfully in the
treatment of bone defects secondary to compression fractures of the
vertebral body.
[0007] One clinical issue associated with vertebroplasty is
containment of the cement within the margins of the defect. For
instance, an osteoporotic compression fracture usually compromises
portions of the cortical bone creating pathways to cement leakage.
Thus, there is a risk of cement flowing beyond the confines of the
bone into the body cavity. Cement leakage into the spinal canal,
for instance, can have grave consequences to the patient.
[0008] Yet another significant risk associated with vertebroplasty
is the injection of cement directly into the venous system, since
the veins within the vertebral body are larger than the tip of the
needle used to inject the cement. A combination of injection
pressure and inherent vascular pressure may cause unintended uptake
of cement into the pulmonary vessel system, with potentially
disastrous consequences including embolism to the lungs.
[0009] One technique which has gained popularity in recent years is
a modified vertebroplasty technique in which a "balloon tamp" is
inserted into the vertebral body via a cannula approach to expand
or distract the fractured bone and create a void within the
cancellous structure. Balloon tamps are inflated using pressurized
fluid such as saline solution. The inflation of a balloon membrane
produces a radial force on the bone and forms a cavity in the bone.
When deflated and removed, the membrane leaves a cavity that is
subsequently filled with bone cement. The formation of a cavity
within the bone allows for the injection of more viscous cement
material which may be relatively less prone to leakage.
[0010] In certain instances, such as the treatment of acute or
mobile fractures, the balloon is also effective at "reducing" the
fracture and restoring anatomic shape to a fractured body. In
particular, balloon dilatation in bone is maximally effective if
the balloon device is targeted inferior to, or below, the fracture
plane. In this instance, the balloon dilatation may distract, or
lift, a fracture bone fragment, such as the vertebral body
endplate.
[0011] In other instances, such as chronic or partially healed
fractures, balloons are less effective at "reducing" the fracture
because radial forces are insufficient. Often the bone in an
incompletely healing fracture is too dense and strong, and requires
more aggressive cutting treatment, such as a drill or reamer tool
to create a sufficient cavity. In these more challenging cases, the
ability to inject bone cement into a cavity created by a balloon or
a reamer in the vicinity of the fracture is typically sufficient to
stabilize the bone and relieve pain, even in the absence of
fracture reduction.
[0012] One limitation to the use of such methods has been the
difficulty in targeting the location at which the cavity should be
created. Known techniques require access to the vertebral body
using straight cutting and reaming tools which are only able to
access a limited region of the vertebral body being treated,
generally only within one side of the vertebral body. A cavity
created using these techniques can only treat one side of a
vertebral body being targeted, resulting in an uneven distribution
of bone cement that cannot completely stabilize the vertebral body.
As a result, multiple entry points on different sides of the
vertebral body are generally required in order to provide a
symmetrical distribution of bone cement around a central axis of
the vertebral body. These multiple entry points significantly
increase the time necessary for the procedure, the portion of the
body being treated, and the amount of bone cement being injected,
and as such can significantly increase the risks associated with
treatment of a patient.
SUMMARY OF THE INVENTION
[0013] The present invention is directed towards novel methods and
devices for preparing a cavity in bone, deploying a
cement-directing stent device, and injecting bone cement into the
device. The methods and devices disclosed herein can allow a cavity
to be created in a vertebral body along a curvilinear pathway,
allowing for a substantially symmetrical distribution of bone
cement over a central vertical axis of a vertebral body. This can
allow a vertebral body to be successfully and completely stabilized
from a single surgical access point and using a single stent
device.
[0014] One aspect of the invention can include a method of
deploying a stent within an enlarged curvilinear void created in a
bony structure. The method can include the steps of: inserting a
distal end of a stent delivery system through a cannula and into a
curvilinear void created in a bony structure, deploying a
self-expanding cement-directing stent within the curvilinear void,
wherein the self-expanding stent is releasably attached to the
distal end of the stent delivery system, attaching a cement
injecting syringe to the proximal end of the stent delivery system,
injecting cement through the stent delivery system and into the
stent, terminating the cement injection when the volume of cement
injected exceeds the interior volume of the expanded stent, and
releasing the stent from the stent delivery system.
[0015] In one embodiment, the stent delivery system can include at
least one of a proximal deployment mechanism, an internal flexible
guidewire, and an internal flexible tube, such as a polymer
extrusion. The self-expanding cement-directing stent can include a
multifilament braided, polymer impregnated, self-expanding,
cement-directing stent collapsed on the distal end of the guidewire
and restrained in a collapsed condition by a tubular polymer
sheath. The self-expanding cement-directing stent can be deployed
by slideably uncovering the tubular sheath to release and expand
the stent within an enlarged curvilinear void. The self-expanding
cement-directing stent can be alternatively or further deployed by
removing the internal flexible guidewire and/or the polymer
extrusion.
[0016] Alternatively, another method of stent deployment eliminates
the need for the tubular sheath. The self-expanding
cement-directing stent is maintained in a collapsed state solely by
the internal flexible guidewire and/or the polymer extrusion. Once
positioned in the enlarged curvilinear void, deployment of the
self-expanding cement-directing stent can be accomplished solely by
removing the internal flexible guidewire and/or the polymer
extrusion.
[0017] In one embodiment, the self-expanding cement-directing stent
can be connectably attached to the proximal deployment mechanism by
a hollow tube assembly. The stent can be released by actuating the
proximal deployment mechanism.
[0018] One aspect of the invention can include a method of
deploying a stent within an enlarged curvilinear void created in a
bony structure. The method can include the step of inserting a
stent catheter assembly into an enlarged curvilinear void through a
cannula and into the curvilinear void created in a bony structure,
wherein the stent catheter assembly can include a proximal
deployment mechanism, an internal flexible guidewire, a
multifilament braided, polymer impregnated, self-expanding,
cement-directing stent collapsed on the distal end of the guidewire
and restrained in a collapsed condition by a tubular polymer
sheath, and connectably attached to the distal end of the
deployment mechanism by a hollow tube assembly.
[0019] The method can further include the steps of deploying the
self-expanding cement directing stent by slideably uncovering the
tubular sheath to release and expand the stent within the enlarged
void within the bony structure, removing the internal flexible
guidewire, attaching a cement filled cement injecting syringe to
the proximal deployment mechanism, injecting cement into the
proximal deployment mechanism through the hollow tube assembly into
the stent, pressurizing the cement to cause the complete filling of
the stent interior, terminating the filling when the volume of
cement injected exceeds the interior volume of the expanded stent,
and releasing the stent from the hollow tube assembly.
[0020] In one embodiment, the self-expanding cement-directing stent
can include a multifilament braided, polymer impregnated,
self-expanding, cement-directing stent. In one embodiment, the
stent delivery system can include a handle and an elongate shaft.
The stent can be releasably attached to a distal end of the
elongate shaft. In one embodiment, the stent is further releasably
attached at a distal end thereof, The stent can be released by
actuating a user control mechanism on the handle. The elongate
shaft can include at least one of an inner shaft, an outer shaft, a
tubular sheath, a flexible guidewire, and an internal polymer
extrusion.
[0021] In one embodiment, prior to the deploying step the
self-expanding cement-directing stent is collapsed on a distal end
of at least one of the inner shaft, the guidewire, and the polymer
extrusion. The self-expanding cement-directing stent can be
deployed by retracting at least one of the inner or outer shaft,
the flexible guidewire, and the polymer extrusion.
[0022] In one embodiment, prior to the deploying step the
self-expanding cement-directing stent can be restrained in a
collapsed condition by the tubular sheath. The self-expanding
cement-directing stent can be deployed by slideably retracting the
tubular sheath to allow the stent to self-expand within the
enlarged curvilinear void. In one embodiment, the deploying step
includes actuating a rotating cam mechanism.
[0023] The invention is also drawn to stent delivery systems and
components thereof adapted for use with any of the methods
described above.
[0024] Another aspect of the invention can include a stent delivery
system for deploying a stent within an enlarged curvilinear void
created in a bony structure. The stent delivery system can include
a handle and an elongate shaft adapted to releasably hold a
self-expanding cement-directing stent at a distal end thereof. The
elongate shaft can include a sheath and at least one of an inner
and an outer shaft. The stent delivery system can also include at
least one user control mechanism adapted to deploy the stent.
[0025] In one embodiment, the at least one user control mechanism
includes a rotating cam mechanism. Actuating the rotating cam
mechanism can retract the sheath towards the handle. In one
embodiment, actuating the rotating cam mechanism simultaneously
extends the distal end of at least one of the inner and the outer
shaft away from the handle.
[0026] In one embodiment, a distal end of the handle can include an
interface element adapted to releasably engage at least a portion
of proximal end of a cannula. The stent delivery system can also
include a stent release mechanism adapted to release the stent from
the elongate shaft.
[0027] Another aspect of the invention can include a user control
mechanism for a stent delivery device. The user control mechanism
can include a support element, at least one cam shaft helically
positioned on the support element, a linear support sleeve, and at
least one pin engaging the cam shaft and the linear support sleeve.
The cam shaft and the linear support sleeve force the pin linearly
along an axial extent of the user control mechanism upon a rotation
of the support element.
[0028] In one embodiment, the at least one pin is attached to an
elongate shaft extending from a distal end of the user control
element. The elongate shaft can include at least one of an inner
shaft, an outer shaft, and a sheath.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] In the drawings, like reference characters generally refer
to the same parts throughout the different views. Also, the
drawings are not necessarily to scale, emphasis instead generally
being placed upon illustrating the principles of the invention. In
the following description, various embodiments of the present
invention are described with reference to the following drawings,
in which:
[0030] FIG. 1A is a schematic side view of a stent including a
plurality of holes, in accordance with one embodiment of the
invention;
[0031] FIG. 1B is another schematic side view of the stent of FIG.
1A;
[0032] FIG. 1C is a schematic rear perspective view of the stent of
FIG. 1A, showing the plurality of holes;
[0033] FIG. 1D is a schematic front perspective view of the stent
of FIG. 1A, showing the plurality of holes;
[0034] FIG. 1E is another schematic rear perspective view of the
stent of FIG. 1A;
[0035] FIG. 1F is another schematic front perspective view of the
stent of FIG. 1A;
[0036] FIG. 2A is a schematic plan view of a delivery system for a
stent, in accordance with one embodiment of the invention;
[0037] FIG. 2B is another schematic plan view of the delivery
system of FIG. 2A;
[0038] FIG. 2C is a photograph of a delivery system inserted in a
patient, in accordance with one embodiment of the invention;
[0039] FIG. 2D is a schematic side view of a cement filled stent
inserted in a vertebral body, in accordance with one embodiment of
the invention;
[0040] FIG. 3A is a schematic plan view of a delivery system and
collapsed stent, in accordance with one embodiment of the
invention;
[0041] FIG. 3B is a schematic perspective view of the handle of the
delivery system of FIG. 3A;
[0042] FIG. 3C is a schematic plan view of the handle of the
delivery system of FIG. 3A;
[0043] FIG. 3D is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the flexible guidewire (e.g.,
nitinol wire) retracted;
[0044] FIG. 3E is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the sheath retracted;
[0045] FIG. 3F is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the flexible guidewire (e.g.,
nitinol wire) and sheath retracted;
[0046] FIG. 3G is a schematic perspective view of a stent coupled
to the delivery system of FIG. 3A, with the sheath retracted;
[0047] FIG. 3H is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the sliding mechanism extended
forward;
[0048] FIG. 3I is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the sliding mechanism retracted to
an intermediate position;
[0049] FIG. 3J is a schematic perspective view of an expanded stent
coupled to the delivery system of FIG. 3A;
[0050] FIG. 3K is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the inner core assembly (i.e.,
polymer extrusion and flexible guidewire) removed;
[0051] FIG. 3L is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with a syringe attached;
[0052] FIG. 3M is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the cement piston inserted to push
through additional cement;
[0053] FIG. 3N is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the cement piston removed;
[0054] FIG. 3O is a schematic perspective view of the handle of the
delivery system of FIG. 3A, with the locking mechanism
unlocked;
[0055] FIG. 3P is a schematic perspective view of the rear of the
handle of the delivery system of FIG. 3A, with the locking
mechanism unlocked;
[0056] FIG. 4A is a schematic side view of a handle for a delivery
system with a rotational cam mechanism, in accordance with one
embodiment of the invention;
[0057] FIG. 4B is a schematic side view of the handle of FIG. 4A
after being turned;
[0058] FIG. 4C is a schematic end view of another handle for a
delivery system with a rotational cam mechanism, in accordance with
one embodiment of the invention;
[0059] FIG. 4D is a schematic side view of the handle of FIG.
4C;
[0060] FIG. 4E is a schematic plan view of the handle of FIG.
4C;
[0061] FIG. 4F is another schematic end view of the handle of FIG.
4C;
[0062] FIG. 4G is a schematic perspective view of a linear sleeve
for the handle of FIG. 4C;
[0063] FIG. 4H is a schematic perspective view of a support element
on a linear sleeve for the handle of FIG. 4C;
[0064] FIG. 4I is a schematic perspective view of the handle of
FIG. 4C;
[0065] FIG. 4J is another schematic perspective view of the handle
of FIG. 4C;
[0066] FIG. 5 is a schematic side view of a handle for a delivery
system with a rotational threaded mechanism, in accordance with one
embodiment of the invention;
[0067] FIG. 6 is a schematic side view of a handle for a delivery
system with a geared mechanism, in accordance with one embodiment
of the invention;
[0068] FIG. 7 is a schematic side view of a handle for a delivery
system with a sliding belt mechanism, in accordance with one
embodiment of the invention;
[0069] FIG. 8A is a schematic perspective view of a handle for a
delivery system with a triggering mechanism, in accordance with one
embodiment of the invention;
[0070] FIG. 8B is a schematic perspective view of the interior cam
mechanism of the handle of FIG. 8A;
[0071] FIG. 9 is a schematic perspective view of a delivery system
inserted in a cannula, in accordance with one embodiment of the
invention;
[0072] FIG. 10A is a schematic end view of a handle for another
delivery system, in accordance with one embodiment of the
invention;
[0073] FIG. 10B is a schematic side view of the handle of FIG.
10A;
[0074] FIG. 10C is a schematic plan view of the handle of FIG.
10A;
[0075] FIG. 11A is a schematic perspective view of the handle of
FIG. 10A;
[0076] FIG. 11B is a schematic perspective view of the handle of
FIG. 11A after rotation of a rotating user control mechanism;
[0077] FIG. 11C is a schematic perspective view of the handle of
FIG. 11B after removal of the top cap;
[0078] FIG. 11D is a schematic perspective view of the handle of
FIG. 11C after depression of sliding of the stent release
buttons;
[0079] FIG. 12A is a schematic sectional side view side view of a
releasable attachment mechanism attached at a distal end of a
collapsed stent, in accordance with one embodiment of the
invention;
[0080] FIG. 12B is a schematic sectional side view of the
releasable attachment mechanism of FIG. 12A after expansion of the
stent;
[0081] FIG. 12C is a schematic sectional side view of the
releasable attachment mechanism of FIG. 12A after detachment from
the distal end of the stent; and
[0082] FIG. 12D is a schematic sectional side view of the
releasable attachment mechanism of FIG. 12A injecting filler
material into the stent after removal of the inner rod.
DETAILED DESCRIPTION OF THE INVENTION
[0083] The present invention discloses methods and apparatus for
introducing a stent into a curvilinear or other shaped cavity
created within the cancellous bone of a fractured vertebral body or
other bony structure. The invention also discloses methods and
apparatus for injecting cement into the stent and into the
surrounding cancellous bone through positioned exit holes in the
stent.
[0084] The methods and apparatus disclosed herein allow for a
covered stent to be safely inserted into the vertebral body through
the same entry profile as current vertebral compression fracture
treatments. Once in place, the delivery apparatus can direct cement
into the stent and through the designated holes into the vertebral
body. This can allow for the controlled flow of cement away from
the spinal canal and towards the anterior side of the vertebral
body. Unlike cardiovascular stent delivery systems, the delivery
systems disclosed herein have a positive attachment to the stent
for cement injection and stent placement adjustability, thus
increasing the stability, controllability, and safety of the system
during surgical procedures.
[0085] In one embodiment of the invention, expansion of a stent in
response to retraction of an outer sheath covering the stent, and
maintaining it in a collapsed configuration, is performed in an
orthopedic rather than cardiovascular environment. In one
embodiment, the delivery system may have certain features that
exhibit some similarity to cardiovascular and endoscopic medical
device designs, but may also have several mechanical additions
specially designed and configured for orthopedic compatibility.
[0086] In one embodiment, the delivery system is configured to
compensate for stent foreshortening in a closed cavity environment.
Foreshortening of a stent occurs when a stent is expanded from a
radially collapsed configuration to a radially expanded
configuration, with the expansion resulting in a reduction in
length as the diameter of the stent is increased. This length
reduction results in the expanded stent being retracted back from
the distal wall of the cavity in which it is deployed, which in
turn results in the expanded stent failing to completely fill the
cavity in which it is deployed. The delivery systems disclosed
herein therefore differ from the usual stent delivery systems that
are used in vascular or duct environments where longitudinal space
is available to allow foreshortening.
[0087] In one embodiment, the stent can be attached to the distal
tip of the delivery system and is not automatically released from
the device during stent expansion. As a result, physicians are able
to pull the stent out of the vertebral body during the surgical
procedure, compress, recover with the outer sheath and redeliver
the stent if the physician is not satisfied with the original
placement. This recovery and redeployment can greatly increase the
chances of correctly placing the stent in the most advantageous,
and safe, position within a patient.
[0088] In one embodiment of the invention, the delivery system has
the ability to retract an outer sheath maintaining the stent in a
collapsed configuration from a side portal in order to minimize the
length of the delivery system. Cement injection back pressures
significantly increase with longer cement injection channels. By
incorporating a slit into the outer sheath to allow the outer
sheath extrusion to pass over the shafts of the delivery system and
be pulled sideways or linearly through the handle, the overall
delivery system length can be reduced. This allows the cement to
travel a shorter distance to fill the stent, and therefore reduces
the injection pressure required to inject cement into the stent at
substantially zero pressure. This reduction in injection pressure
can increase the usability of the delivery system, while reducing
the potential for failure of the injection process, and increasing
the safety of the system.
[0089] In one embodiment, the method of cement injection through
the delivery systems disclosed herein may provide a safer and more
efficient means of treating a vertebral compression fracture than
current vertebral compression fracture treatments. In one
embodiment, cement may be initially injected by a syringe through
the inner shaft of the delivery system. The delivery system can
direct the cement straight into the stent and through the
designated outlet holes in the stent into the surrounding
cancellous bone. Once injection with a syringe becomes difficult,
for example as a result of the cement curing, a solid piston can be
inserted into the inner shaft to deliver more cement. The inner
lumen of the delivery system can, in one embodiment, hold
approximately 1.5 cc of cement from the proximal to the distal end.
The cement piston can also be used to completely clear the inner
shaft of cement to prevent cement back flow out of the pedical.
With the delivery system and stent attachment at the distal tip of
the delivery system, cement injection becomes more controlled than
in more traditional techniques of vertebroplasty and
kyphoplasty.
[0090] Stent
[0091] In one embodiment of the invention, a stent can include a
multifilament co-braided shaped structure and a self-expanding
structure composite which is collapsible to an elongated tubular
shape suitable to fit within a tubular sheath assembled to a novel
delivery catheter. The outer wall of the stent can be impregnated
in preferred regions with a polymer to form a thicker, relatively
less permeable wall. The polymer impregnated co-braided wall is
further perforated with holes or slots in preferred locations. An
example cement directing stent for use with this invention is
disclosed in U.S. Patent Publication No. 2005/0261781 A1 to Sennett
et al., the disclosure of which is incorporated herein by reference
in its entirety. The stent geometry is optimized to fit within a
reamed or balloon-expanded cavity located approximately within the
anterior 2/3 of a vertebral body. The cavity is formed by a
sequential method using a number of specifically designed
instruments. An example stent 100 is shown in FIGS. 1A-1F.
[0092] In one embodiment of the invention, the stent 100 can be
sized to substantially conform to the dimensions of a predetermined
cavity created within a vertebral body. The stent 100 can be
configured to be collapsible, thus allowing delivery of the stent
100 through a relatively small diameter access cannula. The stent
100 can also have a self-restoring shape, allowing the stent to
automatically expand to its original shape, corresponding
substantially with the dimensions of the cavity into which it is
inserted, without the need for inflation of the stent 100 by the
injection of filler material or other fluids or substances. In one
embodiment, the stent 100 may be self-restoring to an expanded
configuration, at least because it is constructed, at least in
part, from a shape-memory material, such as, but not limited to,
nitinol. The stent 100 may be constructed, at least in part, as a
braided structure 110.
[0093] In one embodiment, expansion of the stent 100 does not
generate a distraction force on the end plates of the vertebral
body and does not compact the interior cancellous bone structure of
the vertebral body. Upon expansion of the stent 100 within the
vertebral body, filler material (such as bone cement) can be
injected into the stent 100 to at least partially fill the interior
of the stent 100. In one embodiment, the injection of filler
material does not substantially alter the shape and dimensions of
the stent 100, other than to conform the stent, if necessary, to
the shape of the cavity in which it is disposed.
[0094] In one embodiment of the invention, the wall of the stent
may include at least one hole 120 or permeable region allowing
filler material to leave the interior of the stent 100 and enter
the vertebral body. The at least one hole 120 or porous region can
allow for the controlled and directed distribution of filler
material within the vertebral body. The wall of the stent 100 may
include a plurality of holes of various sizes and/or a plurality of
regions of differing permeability, allowing for a greater or lesser
escape of filler material in different directions. The wall of the
stent 100 may also include at least one baffle or other
non-permeable region preventing the escape of filler material in
certain directions. In general, the total cross-sectional area of
the holes exceeds that of a cement inlet hole 140, to prevent
excess back pressure or buildup of pressure in the interior of the
stent.
[0095] In one embodiment, the stent 100 may have a proximal region
130 that is configured to be releasably mounted to a delivery
system and includes the inlet hole 140 to allow for the injection
of cement. The stent 100 can also have a closed distal region 150
to be positioned away from the delivery system and to be placed
against the distal end of the cavity in which it is placed.
[0096] In one embodiment, the method of treating the patient may
involve external reduction by extension, i.e. physical manipulation
of the patient when placing the patient on the operating table
before treatment of the vertebral fracture site. The method of
treating the patient can also involve stabilizing the vertebral
body, not distracting the upper and lower end plates using the
stent as an expansion device.
[0097] Delivery System
[0098] An example of a delivery system can be seen in FIG. 2A. The
delivery system 200 can include a handle portion 205 at a proximal
end, and a hollow elongate shaft 210 extending towards a distal
end. A stent 215 can be releasably held at the distal end of the
hollow elongate shaft 210.
[0099] In one embodiment of the invention, the delivery system 200
can be configured to releasably couple to a cannula that is
inserted percutaneously from the posterior approach through the
outer tissue of a patient and anchored into the bone of the
vertebral body to a suitable depth. The hollow elongate shaft 210
can be configured to slidably extend through the cannula such that
the stent 215 protrudes from the distal end of the cannula and into
a curvilinear cavity formed within the vertebral body. The stent
may be configured to extend at a specific angle, or along a
predetermined arc, to conform to the axis of the cavity. In an
alternative embodiment, the stent may extend straight out from the
distal end of the hollow elongate shaft 210.
[0100] The flexibility and resiliency of the stent is well adapted
for use in cavities having a variety of shapes, including
curvilinear, cylindrical, tapered, conical, etc. The stent may be
flexible, such that it may be deflected by the walls of the cavity
and therefore conform substantially to the curvature or shape of
the cavity when inserted. In a further alternative embodiment, the
cavity may extend straight out from the distal end of the cannula,
and no curvature or deflection of the stent is required for correct
insertion of the stent into the cavity.
[0101] In one embodiment, a flange 220 and key 225 may be fitted to
the handle portion 205 of the delivery system 200 at the proximal
end of the hollow elongate shaft 210. The flange 220 may enable the
delivery system to be releasably locked to the cannula to ensure
stability of the delivery system 200 during the procedure. The key
225 may be configured to mate with a slot in the cannula to ensure
that the delivery system 200 is inserted into the cannula in the
correct circumferential orientation. In an alternative embodiment,
the delivery system 200 may include a locking mechanism, latch, or
other appropriate means of releasable engagement with the cannula.
In a further alternative embodiment, no means of locking the
delivery system 200 to the cannula may be required.
[0102] In one embodiment, a sheath 230 may be used to releasably
maintain the stent 215 in a collapsed configuration during
insertion through the cannula and into the cavity. The collapsed
configuration may be substantially the same diameter as the
diameter of the hollow elongate shaft 210 (i.e. a diameter
configured to fit slidably through the cannula). The sheath 230 may
be a hollow elongate flexible tube of plastic, fabric, wire mesh,
composite, metal or other appropriate material, that can slideably
extend over the hollow elongate shaft 210 and stent 215 to hold the
stent 215 at a set diameter substantially equal to the diameter of
the hollow elongate shaft 210.
[0103] The proximal end 235 of the sheath 230 may extend through an
exit hole 240 in the handle 205 of the delivery system 200. An
elongate slot may be inserted in a portion of the proximal end 235
of the sheath 230 to allow the sheath 230 to be pulled out through
the exit hole 240 without tearing. In one embodiment, a handle may
be placed on the end of the sheath 230 to assist in pulling the
sheath 230 out through the exit hole 240.
[0104] In use, the sheath 230 is slid over the hollow elongate
shaft 210 and stent 215 to hold the stent 215 in a collapsed
configuration. Once the stent 215 has been inserted through the
cannula and into the cavity, the sheath 230 can be pulled back
through the exit hole 240 in the handle 205. This retracts the
sheath 230 back along the hollow elongate shaft 210 and off the
stent 215. The stent 215 is then free to self-expand to its
original shape, which may, in one embodiment, conform substantially
with the shape of the curvilinear cavity. In one embodiment, a
marking 245 may be placed on the sheath 230 near the proximal end
235 to indicate to a user when the sheath 230 has been retracted
far enough to uncover the stent 215.
[0105] In addition to the sheath 230, or possibly in place of the
sheath 230, a polymer extrusion and/or a flexible guidewire 250 may
be inserted through the handle 205 and hollow elongate shaft 210 to
provide an internal force to extend the distal end of the stent 215
and assist in holding the stent 215 in a collapsed, or partially
collapsed, configuration. The polymer extrusion may be an elongated
hollow polymer shaft made of any flexible polymer such as PEBAX,
Nylon PET or PTFE. The flexible guidewire 250 may be an elongate
solid or hollow rod of stainless steel, aluminum, plastic, or
another appropriate material, that may slideably extend through the
hollow elongate shaft 210 of the delivery system 200, with the
distal end of the flexible guidewire 250 abutting against the
interior distal end of the stent 215 to force the stent
forward.
[0106] In one embodiment, the flexible guidewire 250 may also
include a guidewire handle 255 that can assist the user in pulling
and pushing on the guidewire 250 as required. A mounting element
260 may be releasably connected to the end of the handle 205 with a
bayonet retention feature or other attachment feature and through
which the flexible guidewire 250 passes. The mounting element 260
may also be connected to the polymer extrusion that extends down to
the stent 215 and is disposed coaxially between the flexible
guidewire 250 and the hollow elongate shaft 210 of the delivery
system 200. This extrusion may be used, for example, to provide a
smooth, low friction boundary between the guidewire 250 and the
hollow elongate shaft 210. The polymer extrusion may be of a length
such that the extrusion also assists in maintaining the stent 215
in a collapsed configuration prior to insertion and deployment in
the cavity. The mounting element 260 may be used to cover a luer
lock, or other mounting feature, that may be used to releasably
hold a syringe once the inner core assembly (i.e., polymer
extrusion and guidewire 250) has been removed.
[0107] The inner core assembly (i.e., polymer extrusion and
guidewire 250) may provide multiple functions for the delivery
system 200. For example, the inner core assembly (i.e., polymer
extrusion and guidewire 250) may be used to assist in maintaining
the stent 215 in a collapsed configuration prior to insertion and
deployment in the cavity. The inner core assembly (i.e., polymer
extrusion and guidewire 250) may also be used to counteract any
foreshortening of the stent 215 that may occur during
expansion.
[0108] In one embodiment, a sliding mechanism 265 can also be used
to counteract foreshortening of the stent 215 as a result of
expansion within the cavity. The sliding mechanism may be fixedly
coupled to the hollow elongate shaft 210 of the delivery system
200, and be slidably coupled to the handle 205 of the delivery
system 200. By sliding the sliding element 265 forward, the entire
hollow elongate shaft 210 and attached stent 215 can be pushed
forward, thus pushing the distal end of the expanded stent 215
towards the distal end of the cavity. After the stent 215 has been
pushed to the end of the cavity, the sliding element 265 can be
slid backwards by a small amount to counteract any foreshortening
of the proximal end of the stent 215 that may result from the
pushing process. A releasable locking mechanism 270, including a
spring mounted locking element 275, can be used to ensure that the
sliding element 265 is locked in place when not needed. In one
embodiment, markings may be placed on the handle 205 to indicate
the length of travel of the sliding element 265.
[0109] Once a stent 215 has expanded and been correctly positioned
within a cavity, the stent 215 may be filled with cement, cement
analogue, or other filler material, by fitting a syringe to the
luer lock, or other locking mechanism at the proximal end of the
hollow elongate shaft 210, after the inner core assembly (i.e.,
polymer extrusion and guidewire 250) has been removed. The cement
can then flow through the hollow elongate shaft 210 and into the
interior of the stent 215, after which it can flow into the
vertebral body through the carefully positioned holes in the stent
215.
[0110] Once the stent has been filled, the stent can be released
from the delivery system 200 and the system removed from the
patient. A locking mechanism 280 may be included in the handle 205
of the delivery system 200 to releasably hold the stent 215 to the
hollow elongate shaft 210. The locking mechanism 280 may be
attached to an elongate element that is attached at its distal end
to the proximate end of the stent 215. The locking mechanism 280
may also include a slider 285, or a switch, clasp, or other user
interface element, to unlock the stent 215 from the elongate
element and/or hollow elongate shaft 210 once the stent has been
correctly positioned and filled. In one embodiment, a pin 290 may
be removably inserted into the locking mechanism 280 to ensure that
the stent 215 is not released accidentally.
[0111] It should be noted that at all steps of a method using the
above-identified delivery system 200, medical imaging techniques,
such as fluoroscopy, may be used to image the interior of the
vertebral body and confirm the location and status of the stent
215, cement, and cavity.
[0112] An example a delivery system 200 with the sheath 230
retracted and the stent 215 expended is shown in FIG. 2B. An
example of this delivery system 200 inserted into a patient can be
seen in FIG. 2C. A cross-section of a cement filled stent 215
inserted into a vertebral body 292 is shown in FIG. 2D. In this
figure, large arrows 294 indicate the direction of the cement
leaving through holes 296 in the stent 215 in order to stabilize a
fracture 298. Small arrows correspond to areas of lower
permeability of the stent 215, through which nominal amounts of
cement leave the stent 215 to further anchor the stent 215 and fill
any remaining voids in the cavity.
[0113] Method of Use
[0114] An embodiment of the invention can include a method of using
the delivery systems described herein to insert and deploy a stent
device into a cavity created in a vertebral body. The cavity may be
a curvilinear cavity. In an alternative embodiment, the cavity may
be of any appropriate size and shape, with a stent selected to be
configured to substantially conform to the size and shape of the
cavity created.
[0115] In one embodiment of the invention, a procedure for using
the devices disclosed herein can be used to produce a curvilinear
cavity within a vertebral body, and place a stent within the cavity
created within the vertebral body. The stent can be a
self-expanding, covered stent that allows interdigitation and
prevents leakage of bone cement in undesired directions. In one
embodiment, a single stent can be placed at a mid-line location of
a vertebral body, rather than placing multiple stents on either
side of the mid-line, thus reducing the time and fluoroscopy
exposure require during a surgical implantation procedure.
[0116] In one embodiment, the method of creating a cavity for
within a vertebral body, or other bony body, can include first
creating a posterior pathway to the vertebral body, using a
extrapedicular or intrapedicular approach, with a Jamshidi needle
and/or K-wire. This may be performed, for example, using a dual
C-arm technique to place and medialize the Jamshidi needle/K-wire
to the fullest extent.
[0117] A working channel and trocar assembly can then be inserted
along the pathway created by the Jamshidi needle/K-wire. This can
be performed, for example, by locking the trocar into the working
channel, inserting the working channel into the pathway, and
tapping the assembly into place until the distal tip of the trocar
and working channel extends, in one embodiment, 1-3 mm beyond the
posterior wall of the vertebral body. The trocar can then be
removed, leaving the open working channel in place.
[0118] A curved pathway through the vertebral body can then be
created using a curved drill. This may be achieved using any of the
drill arrangements described herein. In one embodiment, the drill
depth markings at the user interface are set to "0"mm prior to
insertion into the working channel. The drill can then be locked
into the working channel with the key facing in the medial
direction, thus ensuring the correct direction of curvature of the
drill within the vertebral body. The handle of the drill can then
be rotated to advance the drill tip into the vertebral body, with
fluoroscopy, or some other appropriate technique, used to determine
when the desired depth of penetration is achieved. The drill can
then be removed and the depth markings on the user interface
recorded. In one embodiment, the drill tip is oriented in the
contralateral anterior quadrant of the vertebral body, thus
assuring proper cavity positioning and bilateral cement
filling.
[0119] In one embodiment, a larger cavity can then be created
within the vertebral body by reaming out the hole created by the
curved drill with a curved reamer. This may be achieved, for
example, by first setting the depth markings on the user interface
of the reamer to match those recorded for the drill depth, thus
assuring that the reamer is positioned correctly within the
vertebral body. The reamer can then be advanced fully into the
pathway created by the drill and locked into the working channel,
with the position of the reamer confirmed using fluoroscopy or some
other appropriate technique. The blade of the reamer can then be
opened, for example by rotating a portion of the handle of the
reamer, and reaming can be carried out by rotating the handle. In
one embodiment, the reamer may be stopped approximately 1-3mm
before approaching the distal tip of the working channel, with the
position confirmed by fluoroscopy, or some other appropriate
technique. The blade can then be closed (for example by rotating a
portion of the handle in the opposite direction), and the reamer
removed. In one embodiment, due to blade deflection, the cavity
created by the reamer can have a slight taper from the distal end
to the proximal end.
[0120] Once a cavity has been created, a stent delivery system can
be locked into the working channel to correctly position a stent
within the vertebral body. Once the stent has been positioned, a
sheath covering the stent can be removed to deploy and expand the
stent, and cement can be injected into the stent by attaching a
syringe to the proximal end of the delivery system. The desired
amount of cement can be injected into the stent with fluoroscopy,
or some other appropriate technique, being used to monitor the flow
of cement into the stent. Once the requisite amount of cement has
been injected, the stent can be released from the delivery system
and the delivery system removed from the working channel, thus
leaving the stent in place within the vertebral body. The working
channel can then be removed and the access pathway sutured or
otherwise closed.
[0121] One example embodiment may include inserting a delivery
system 200 into the cannula such that the covered stent is extended
beyond the distal end of the cavity and into the curvilinear
cavity. An example of a delivery system prior to insertion into a
cannula is shown in FIGS. 3A-3C. Once the delivery system 200 is
fully inserted within the cannula, the delivery system 200 can
engage with, and be locked in place by, a locking element
associated with the cannula. In one embodiment of the invention,
the delivery system 200 may be extended through the cannula until a
user can feel resistance to the forward movement, indicating that
the end of the collapsed stent is abutting against the distal end
of the cavity created within the vertebral body. In an alternative
embodiment, the length of the cavity may be carefully measured such
that the end of the collapsed stent will automatically extend to
the end of the cavity upon insertion of the delivery system 200. In
addition to these techniques, or in place of these techniques,
representative fluoroscopic photos or movies, or use of other
appropriate medical imaging techniques, may be taken to ensure the
correct placement of the stent within the cavity.
[0122] Once the stent has been correctly positioned within the
cavity in its collapsed configuration, it may be expanded within
the cavity. In one embodiment, the inner core assembly (i.e.,
polymer extrusion and guidewire 250) inserted through the center of
the delivery system 200 and abutting against the distal end of the
stent may be pulled back, for example by pulling on a handle 255
attached to the flexible guidewire 250 and twisting off the bayonet
retention feature of the mounting element 260 attached to the
polymer extrusion, thus relieving the force on the distal end of
the stent that is assisting in maintaining the stent in a collapsed
configuration. In one example embodiment, the flexible guidewire
250 and handle 255 may be pulled back by approximately two inches,
or by a greater or lesser distance, as required. In an alternative
embodiment, the flexible guidewire 250 and handle 255 may be
removed completely. In a further alternative embodiment, there is
no need for the inner core assembly (i.e., polymer extrusion and
guidewire 250) to be inserted within the delivery system 200, with
the sheath 230 alone being sufficient to maintain the stent in a
fully collapsed configuration. An example of a flexible guidewire
250 and handle 255 being retracted can be seen in FIG. 3D.
[0123] Once the force on the distal end of the stent, provided by
the flexible guidewire 250 and/or polymer extrusion, has been
removed, the stent is ready to be expanded. Expansion of the stent
can be executed by retracting the sheath 230, for example by
pulling on a handle attached to the sheath, by a predetermined
amount. A mark 245 may be placed on the sheath 230 to indicate when
the sheath 230 has been pulled back by the correct amount.
Retracting the sheath 230 removes the external restrictive force on
the stent and allows it to self-expend to its preformed, free-state
configuration. This may, in one embodiment of the invention,
substantially conform to the size and shape of the cavity. An
example of a sheath 230 after being retracted can be seen in FIGS.
3E and 3F. In an alternative embodiment, the sheath 230 can be
removed prior to the polymer extrusion being removed. An example of
a stent 215 with the sheath 230 retracted but with the polymer
extrusion remaining in place and extended to the distal end of the
stent 215 can be seen in FIG. 3G.
[0124] In one embodiment of the invention, expansion of the stent
215 can also result in a certain amount of foreshortening at the
distal end of the stent 215. This foreshortening, which is caused
by the increase in the diameter of the stent 215 as it expands
resulting in a responsive decrease in the length of the stent 215,
may retract the end of the stent 215 slightly from the distal end
of the cavity. This may be compensated for by providing a force to
push the entire stent 215 forward until the distal end of the
expanded stent 215 abuts against the distal end of the cavity. This
may be achieved through the use of a sliding mechanism 265 that is
configured to allow for the extension and retraction of the entire
stent 215 and elongated shaft 210 arrangement along the axis of the
shaft. By releasing the locking mechanism 270 on this sliding
mechanism 265, the stent 215 and elongated shaft 210 can be pushed
forward by the required amount. The sliding mechanism 265 can then
re-engage the locking mechanism to lock the stent at a final
position. An example of the sliding mechanism 265 pushed forward
within the handle 205 can be seen in FIG. 3H.
[0125] In one embodiment, forcing the expanded stent 215 forward
may result a certain amount of foreshortening of the stent 215 at
its proximal end (i.e. the end attached to the elongated shaft 210
of the delivery system 200). Here, after forcing the stent 215
forward using the sliding mechanism 265, the sliding mechanism 265
may be retracted by a small amount to counteract any foreshortening
at the proximal end of the stent 215. Again, the sliding mechanism
265 may be locked into position once the stent 215 has been
correctly positioned. As before, fluoroscopic images, or other
appropriate medical images, may be taken to confirm the positioning
and expansion of the stent at the distal end of the cavity. In one
embodiment of the invention, the polymer extrusion may also be used
to extend the expanded stent after foreshortening due to the
expansion. An example of the sliding mechanism 265 retracted after
being pushed forward within the handle 205 can be seen in FIG. 3I.
An example of a fully expanded stent 215 coupled to a hollow
elongated shaft 210 with a sheath 230 retracted can be seen in FIG.
3J.
[0126] As mentioned above, the polymer extrusion can perform the
function of collapsing the stent by stretching the stent out
longitudinally or axially, by applying a force in that direction
from within the stent. The proximal end of the stent is fixed to
the elongate shaft 210 and the distal end of the stent is stretched
and held in place by the polymer extrusion which is locked in
position to the handle 205 by the mounting element 260. With the
stent collapsed, it can be moved easily down the working channel,
thereby eliminating the need for a sheath in the delivery
system.
[0127] After correct positioning of the expanded stent 215, the
polymer extrusion can be removed completely from the delivery
system 200 by releasing and retracting the mounting element 260
from the handle portion 205. Removing the polymer extrusion leaves
a hollow shaft 210 through the center of the delivery system 200
and into the interior of the expanded stent 215. This hollow shaft
can then be used for the injection of cement, or other material,
into the stent. An example of the delivery system with the polymer
extrusion removed can be seen in FIG. 3K.
[0128] Injection of cement into the stent may be performed by
releasably connecting the end of a syringe 310 to the hollow shaft
at the point vacated by the polymer extrusion mounting element 260.
In one embodiment of the invention, a 10 cc threaded syringe may be
used, although in alternative embodiments, any appropriate
injection device may be utilized. In one embodiment, the proximal
end of the hollow shaft may include a luer lock 320, or other
releasable locking arrangement, that may engage the end of the
syringe 310 and engage it with the hollow shaft 210. An example of
a syringe 310 attached to the handle 205 of the delivery system 200
can be seen in FIG. 3L. Alternatively, instead of directly rigidly
connecting the syringe 310 to the handle 205, a rigid or flexible
extension tube can be interdisposed between the syringe 310 and the
handle 205. The extension tube allows the physician to have his
hands out of the fluoroscopic field and also provides the
opportunity to reorient the syringe 310, e.g., by forming an
"elbow" or other angular connection, so that the syringe 310 is not
fixedly cantilevered axially from the delivery system 200.
[0129] Once the syringe 310 is in place, the cement, or other
material, such as a cement analogue, can be injected into the
hollow shaft 210 of the delivery system 200 and into the expanded
stent 215. Injection of cement may be continued until the stent 215
is completely filled and cement flows out of the designated holes
in the stent into the vertebral body. Once enough cement has flowed
out of the stent 215 and into the vertebral body to provide the
required level of interdigitation between the stent 215 and
vertebral body, the injection can be stopped. Again, fluoroscopic
images, or other appropriate medical images, may be taken to
confirm that the stent has been filled and the required amount of
cement has flowed out into the vertebral body at the correct
positions.
[0130] In one embodiment of the invention a cement piston 325 may
be used to push additional cement in the hollow shaft 210 into the
stent 215, for example when high cement viscosity has resulted in
incomplete filling of the cavity. This may be achieved by simply
detaching the syringe 310, and pushing the cement piston 325 back
into the hollow shaft 210 to force the additional cement in the
shaft 210 into the stent 215. This may be important if the
physician is not satisfied with the amount of cement filling prior
to removal. In one embodiment, the hollow shaft 210 can hold 1.5 cc
of cement, or other material, with the cement piston 325 capable of
pushing any percentage of that volume into the stent 215, as
required. Once the correct amount of cement has been injected into
the stent 215, the cement piston 325 can again be removed. An
example of the cement piston 325 forcing cement through the shaft
210 can be seen in FIG. 3M. An example of the handle 205 of the
delivery system 200, after the cement piston 325 has been removed
again, can be seen in FIG. 3N.
[0131] After the stent 215 has been filled with cement, and the
correct amount of cement has exited the stent 215 through the exit
holes to interdigitate with the vertebral body, the stent 215 can
be released from the delivery system 200 and the delivery system
200 removed. In one embodiment of the invention, a locking
mechanism 280 may be used to hold the stent 215 onto the delivery
system 200. This locking mechanism 280 may include any appropriate
means of releasably engaging the proximal end of the stent,
including, but not limited to, a clamping mechanism, a grasping
mechanism, sliding mechanism, a pressure fit between an outer
shaft, the proximal end of the stent, and the inner hollow shaft,
or any other appropriate mechanism. In one embodiment, the locking
element 285 may include a slide, switch, or other element at the
proximal end of the delivery system, allowing the locking mechanism
to disengage from the stent when required. A removable pin 290, or
other locking device, may be inserted into the delivery system 200
to ensure that the delivery system 200 is not disengaged from the
stent 215 inadvertently, before the cement has been fully injected.
An example of the locking mechanism 280 after the pin 290 has been
removed and the locking mechanism 280 opened is shown in FIGS. 3O
and 3P.
[0132] Once the stent has been released from the delivery system,
the delivery system can be unlocked and removed from the cannula.
After this, the cannula may be removed and the surgical incision
closed.
[0133] In an alternative embodiment, a delivery system including a
handle adapted to move multiple components of the delivery system
with a movement of a single user control mechanism can be used to
deploy a stent within a cavity created within a vertebral body.
This user control mechanism can include a mechanism such as, but
not limited to, a rotating mechanism, a sliding mechanism, a
trigger mechanism, or any other appropriate mechanical, electrical,
and/or magnetic mechanism.
[0134] Employing a user control mechanism to control a number of
functions of the delivery system can both simplify and speed up the
deployment process, while reducing the number of steps that need to
be performed by a user during the deployment process. This can
increase the efficiency of the delivery system while increasing the
safety of the deployment methods for a patient being treated. In
one embodiment, a user control mechanism can control the retraction
of a sheath covering the stent, the movement of an inner shaft,
and/or the movement of an outer shaft. The inner shaft can include,
but is not limited to, a flexible guidewire, a hollow flexible
shaft, and/or another appropriate elongate element configured to
extend through the interior of an outer shaft. The outer shaft can
include, but is not limited to, a hollow elongate shaft configured
to releasably engage the stent at its distal end.
[0135] In an alternative embodiment, additional and/or different
functions of the delivery system can be controlled by a single user
control mechanism. These functions can include, but are not limited
to, injecting filler material such as cement into the stent,
releasing the stent, locking, and/or unlocking, the delivery system
to/from the cannula, curving the distal end of the flexible shaft
to facilitate deployment of the stent within a curved cavity,
and/or any other appropriate function of a stent delivery
system.
[0136] In one embodiment, a user control mechanism is adapted to
retract the outer sheath of the elongate shaft of a delivery system
to allow the stent to be fully deployed within a cavity in a
vertebral body. At the same time, the inner and outer shafts of the
elongate shaft are moved forward to compensate for any
foreshortening of the stent during retraction of the sheath, as
described above. This allows the stent to be deployed in its
expanded configuration at the full distal extent of the cavity. The
user control mechanism can be configured to move the sheath and the
inner and outer shafts simultaneously in opposite directions by set
amounts, with the sheath being retracted towards the handle of the
delivery system while the inner and outer shafts are extended
outwards away from the handle.
[0137] The distance by which each of the sheath and the inner and
outer shaft should be moved relative to each other is dependent
upon factors that can include the size and shape of the stent and
the cavity in which the stent is being deployed. For example, in
one embodiment, the sheath can be retracted by a distance equal to
or greater than the length of the stent to ensure that it is fully
retracted from the stent in order to allow the stent to expand
fully. The inner and outer shafts, in contrast, can be extended by
a distance equal to the foreshortening of the stent as it expands
from its collapsed configuration to its expanded configuration. In
one embodiment, the inner and outer shafts can be extended out from
the handle by the same distance. In an alternative embodiment, the
inner shaft and the outer shaft can be extended out from the handle
by different distances.
[0138] Example user control mechanisms for moving multiple
components of a delivery system can be seen in FIGS. 4A-8B.
[0139] FIGS. 4A and 4B show a handle 400 for a delivery system with
a rotational cam mechanism 410 before and after being rotated. The
rotational cam mechanism 410 includes three separate slotted cam
shafts wrapped helically on a support element 420 surrounding the
central shaft 425 of the handle 400. An outer grip 430 covers the
support element 420 and central shaft 425 and engages with the
support element 420. Pins associated with each of the outer shaft,
the inner shaft, and the sheath engage with the slotted cam shafts
such that a rotation 435 of the support element 420 will force the
pins axially along the central shaft of the delivery device in a
direction and distance controlled by the angle and direction of
each slotted cam shaft.
[0140] More specifically, a first slotted cam shaft 440 engages
with a first pin 445 attached to the outer shaft of a delivery
system. A second slotted cam shaft 450 engages with a second pin
455 attached to the inner shaft of the delivery system. And, a
third slotted cam shaft 460 engages with a third pin 465 attached
to a sheath. As a result, as the outer grip 430 is rotated about
the central shaft 425 of the handle 400, the first pin 445 and
second pin 455 will be forced axially forward 470 toward the distal
end of the handle 400, resulting in the inner shaft and outer shaft
being extended outwards from the distal end of the handle 400 (and
therefore compensating for any foreshortening of the stent during
deployment). Simultaneously, the third pin 465 will be pulled
axially rearwards 475 toward the proximal end of the handle 400,
resulting in the sheath being pulled rearwards 475 towards the
handle 400 (and therefore exposing the stent).
[0141] In one embodiment, the helical paths for each of the inner
shaft and outer shaft have the same angle, resulting in the distal
ends of the inner shaft and outer shaft each being forced forward
470 the same distance. In an alternative embodiment, the helix
paths for each of the inner shaft and outer shaft may be different,
resulting in the distal ends of the inner shaft and outer shaft
being forced forward 470 by a different amount. In a further
alternative embodiment, at least one of the inner shaft and outer
shaft may be stationary.
[0142] Additional axially slotted cam shafts can be located at the
distal end of the first slotted cam shaft 440 and third slotted cam
shaft 460, allowing the first pin 445 and third pin 465 to remain
in the same axial position while the second pin 455 is moved
rearwards 475 by pulling the outer grip 430 rearwards 475 towards
the proximal end of the handle 400 of the delivery system after the
rotation of the outer grip is completed. By having axial slots of
different lengths, the pins can be moved axially by different
distances when the outer grip is pulled rearwards 475 towards the
proximal end of the handle. For example, the first axial slotted
cam shaft 480 (associated with the outer shaft) is shorter than the
second axial slotted cam shaft 485 (associated with the sheath), so
that when the outer grip 430 is pulled rearwards 475, the second
pin 455 is moved rearwards 475 along with the outer grip 430, the
first pin 445 remains stationary until it connects with the end 490
of the first axial slotted cam shaft 480, after which it moves
rearwards 475 along with the outer grip 430, and the third pin 465
remains stationary throughout the entire axial rearward 475 motion
of the outer grip 430. In alternative embodiments, different
lengths of axial cam shafts can be associated with any of the pins,
allowing for different rearward travel distances, as desired. By
moving the outer shaft back a certain distance after being pushed
forward, while leaving the inner shaft extended, the stent can be
stretched out and fully deployed without the distal end of the
stent being pulled back from the distal end of the cavity. In an
alternative embodiment, there are no axial cam shafts.
[0143] In one example embodiment, the outer grip 430 can be rotated
through approximately 120.degree. to fully move the sheath, inner
shaft, and outer shaft (and thus deploy the stent). In an
alternative embodiment, a larger or smaller rotation of the outer
grip 430, for example between 90.degree. and 360.degree., can be
used.
[0144] Another example of a handle 400 for a delivery system with a
rotational cam mechanism 410 is shown in FIGS. 4C-4J. In this
embodiment, the delivery system includes a handle portion 400 and a
hollow elongate shaft (not shown) extending from the distal end of
the handle 400. The hollow elongate shaft can include a distal end
adapted to support and deploy a stent within a cavity created
within a vertebral body. The hollow elongate shaft can include an
inner shaft and an outer shaft adapted to engage a stent,
releasably positioned at the distal end of the elongate shaft. A
sheath can be positioned over the outer shaft and extend over the
stent to maintain the stent in a collapsed configuration during
insertion through the cannula and into the cavity.
[0145] As with the embodiment of FIGS. 4A and 4B, the rotational
cam mechanism 410 includes three separate slotted cam shafts
wrapped helically on a support element 420 surrounding the central
shaft 425 of the handle 400. An outer grip 430 covers the support
element 420 and central shaft 425 and engages with the support
element 420. Pins 445, 455, 465 (associated with each of the outer
shaft, the inner shaft, and the sheath) engage with the slotted cam
shafts 440, 450, 460 such that a rotation 435 of the support
element 420 will force the pins 445, 455, 465 axially along the
central shaft of the delivery device in a direct and distance
controlled by the angle and direction of each slotted cam shaft
440, 450, 460. In one embodiment, the pins 445, 455, 465 are
positioned within a linear support sleeve 492 that is configured to
ensure that the pins 445, 455, 465 can only move axially, either
forwards 470 or backwards 475, along the length of the handle 400.
A schematic perspective view of the linear support sleeve 492
engaging one of the pins is shown in FIG. 4G, with FIG. 4H showing
the support element 420 positioned on the linear support sleeve
492.
[0146] A single axial slotted cam shaft 495 is located at the
distal end of the first slotted cam shaft 440 and third slotted cam
shaft 460, allowing the first pin 445 and third pin 465 to moved
rearwards 475 together. A removable cap 497 is placed on the
proximal end of the handle 400 to cover a luer lock 498 adapted for
engagement with a filler material delivery device, such a
syringe.
[0147] A stent release button 482 is located on the handle 400 to
actuate disengagement of the stent from the elongate shaft once
deployment and filling of the stent is completed. The stent release
button 482 can be depressed and slid rearwards 475 towards the
proximal end of the handle 400 (i.e. away from the elongate shaft)
to release the stent from the elongate shaft. In an alternative
embodiment, two stent release buttons located opposite each other
on either side of the handle 400 can be used. In a further
alternative embodiment, any appropriate user interface elements
including, but not limited to, a dial, a switch, a sliding element,
or a button, can be used to activate the detachment of the stent
from the elongate shaft, and/or to perform any other required
functions.
[0148] FIG. 5 shows a handle 500 for a delivery system with a
rotational threaded mechanism 510. The rotational cam mechanism 510
includes two separate threads wrapped helically on a support
element 520 surrounding the central shaft 525 of the handle 500. An
outer grip 530 covers the support element 520 and central shaft 525
and engages with the threads on the support element 520. A first
thread 540 is associated with the sheath of the delivery system,
while a second thread 550 is associated with at least one of the
inner shaft and outer shaft of the delivery system. A slotted
control button 560 can provide a user control for additional
functions of the delivery system.
[0149] In operation, a rotation of the outer grip 530 will drive
the sheath (associated with the first thread 540) in an axially
rearward 575 direction, while the inner and/or outer shaft
(associated with the second thread 550) will be driven in an
axially forward 570 direction. The helical angle of each thread
will determine how far each element is moved axially through the
rotation of the outer grip 530. In an alternative embodiment,
larger or smaller helical angles can be used to move one or more
elements by any required distance, as appropriate. In addition,
more threads, at any required helical angle, can be incorporated
into the rotational threaded mechanism 510 to control additional
elements of the delivery system.
[0150] In an alternative embodiment, a geared mechanism can be used
to control the movement of the inner shaft, the outer shaft, the
sheath, and/or any other appropriate element of the delivery
system. The geared mechanism can include a number of gear
arrangements, including any appropriately configured and sized
gears to move the shafts and/or sheath in different directions and
by different distances, as required sequentially or simultaneously.
An example geared mechanism 610 can be seen in FIG. 6.
[0151] FIG. 6 shows a handle 600 for a delivery system with a
geared mechanism 610. The geared mechanism 610 includes a first
gear arrangement 620, engaging the sheath, and a second gear
arrangement 630 for controlling the movement of one of more of the
inner and outer shafts. In operation, a pin 640 can be moved in a
rearward direction 675 by a user, thus pulling the sheath rearwards
475 by a distance corresponding to the length of the slot 650. The
first gear arrangement 620 will be driven by the movement of the
pin 640, which will in turn drive the second gear arrangement 630
and push the inner shaft and/or outer shaft in a forward direction
670. Through careful selection of the slot 650 and gearing
arrangements 620, 630, the sheath and the inner and/or outer shafts
can be moved by any appropriate distance and in either the forward
670 or rearward 675 direction. Different gearing arrangements to
drive additional and/or different elements can be used, as
appropriate. In an alternative embodiment, a dial associated with a
gearing element, or other appropriate user control, can be used
instead of, or in addition to, the pin.
[0152] FIG. 7 shows a handle 700 for a delivery system with a
sliding belt mechanism 710. The sliding belt mechanism 710 includes
a sliding outer grip 720 that is coupled to an inner sliding belt
arrangement 730 that forces an inner element 740 in a forward 770
direction as the sliding outer grip 720 is pushed in a rearward 775
direction by a user.
[0153] More specifically, the sheath is attached to the sliding
outer grip 720, while the inner shaft and outer shaft are connected
to the inner element 740. By coupling the sheath, inner shaft,
and/or outer shaft of the elongate shaft 750 to either the sliding
outer grip 720 or the inner element 740, each shaft and sheath can
be moved forwards 770 or rearwards 775, as required. The sliding
belt mechanism can provide simultaneous movement of the shafts
and/or sheath, but may also provide sequence in the movement of the
shafts and/or sheath by delaying one function through the belt
arrangement 730. As before, a luer lock 760 can be placed at a
proximal end of the handle 700 to provide a coupling element for a
cement deliver device, such as a syringe.
[0154] FIGS. 8A and 8B show a handle 800 for a delivery system with
a triggering mechanism 810. The triggering mechanism 810 includes
three separate slotted cam shafts positioned on a pair of cam
plates 820 within a trigger 825 that is pivotably connected to a
support element 830. Pins associated with each of the outer shaft,
the inner shaft, and the sheath of the elongate shaft 815 engage
with the slotted cam shafts such that a closing of the trigger 825
will force the pins axially along the central shaft 835 of the
delivery device in a direct and distance controlled by the angle
and direction of each slotted cam shaft. This configuration can
result in a simple mechanical delivery system that is easy to
use.
[0155] More specifically, a first slotted cam shaft 840 engages
with a first pin 845 attached to the outer shaft of a delivery
system. A second slotted cam shaft 850 engages with a second pin
855 attached to the inner shaft of the delivery system. And, a
third slotted cam shaft 860 engages with a third pin 865 attached
to a sheath. As a result, as the trigger 825 is closed by being
pivoted 885 into the support element 830 about a pivot point 880,
the first pin 845 and second pin 855 will be forced axially forward
870 toward the distal end of the handle 800, resulting in the inner
shaft and outer shaft being extended outwards from the distal end
of the handle 800 (and therefore compensating for any
foreshortening of the stent during deployment). Simultaneously, the
third pin 865 will be pulled axially rearwards 875 toward the
proximal end of the handle 800, resulting in the sheath being
pulled rearwards 875 towards the handle 800 (and therefore exposing
the stent).
[0156] The first slotted cam shaft 840 includes a bend 890,
resulting in the first pin 845 (and therefore the outer shaft)
being moved forward 870 initially before being moved in a rearward
direction 875 during a second portion of the closing motion. In
alternative embodiments, any one or more of the cam shafts can be
curved, bent, and/or angled in any appropriate manner to produce
the required forwards and/or rearward movement of each element of
the delivery system. In a further alternative embodiment, none of
the cam shafts include a bend.
[0157] As before, a luer lock 895 can be placed at a proximal end
of the handle 800 to provide a coupling element for a cement
delivery device, such as a syringe. In one embodiment, a bump 892
on a rear portion of one or both of the cam plates 820 can engage
and force the release of an end cap on the handle 800, thus
exposing the luer lock 895 and prompting the user to begin the next
stem of the process. In an alternative embodiment, no bump is
required, and the end cap of the handle 800 is instead removed
manually.
[0158] In one embodiment, the delivery system may include a locking
mechanism adapted to releasably lock the delivery system within a
cannula in a required circumferential orientation, to ensure the
correct positioning of the stent within the cavity created within
the vertebral body. In one embodiment, a spring loaded locking
mechanism on the cannula may engage a portion of the handle of the
delivery system to releasably lock it in place, with one or more
buttons, switches, knobs, or other appropriate user elements,
either on the cannula or on the handle of the delivery system,
releasing the locking mechanism when the delivery system is to be
removed. In one embodiment, the cannula can include a sliding
element adapted to engage a protruding flange at a distal end of a
handle of a delivery system to releasably lock the delivery device
into the cannula. An example cannula 900 including a sliding
element 910 for releasably engaging a protruding flange of a
delivery system 920 can be seen in FIG. 9. In further embodiments,
any other appropriate means of releasably locking the delivery
system to the cannula in a required circumferential configuration
can be used.
[0159] In one embodiment, a key may be positioned on the hollow
elongate shaft to mate with a slot in the cannula to ensure that
the delivery system is inserted into the cannula in the desired
orientation. In an alternative embodiment, at least a portion of
the distal end of the handle of the delivery system can be
configured to mate with a portion of the cannula, thus ensuring the
positioning of the delivery system in the correct orientation.
[0160] In one embodiment, as described above, the delivery system
can be used to deploy a stent within a cavity created within a
vertebral body, wherein the handle is adapted to control multiple
components of the delivery system with a movement of a single user
control mechanism, such as a rotation, sliding, or triggering of a
user control mechanism.
[0161] Another example delivery system 1000, including a rotating
user control mechanism 1040 on the handle 1010, can be seen in
FIGS. 10A to 10C. The rotating user control mechanism can include,
but is not limited to, a rotational cam mechanism or a rotational
threaded mechanism. In an alternative embodiment, a gear mechanism,
a sliding belt or triggering mechanism, or any other appropriate
mechanism, as described herein, can be used in place of the
rotating user control mechanism 1040 to move the inner shaft, outer
shaft, and/or sheath, as required.
[0162] As with certain other embodiments of the invention described
herein, the delivery system 1000 includes a handle 1010, an
elongate shaft 1020, including a key component 1025, a top cap
1030, and a number of user interface elements. The user interface
elements include a rotating user control mechanism 1040 and two
stent release buttons 1050. In an alternative embodiment, a lesser
or greater number of stent release buttons can be used. In one
embodiment, the stent release buttons 1050 can be replaced by one
or more switches, knobs, sliding elements and/or other appropriate
user elements, or combinations thereof, as required.
[0163] In one embodiment, one or more additional user input
mechanisms 1060 can be incorporated into the handle 1010. These
user input mechanisms 1060 can include, but are not limited to,
delivery system release mechanisms, stent deployment and/or release
mechanisms, a mechanism for controlling the curvature of a distal
end of one or more of the elongate shafts, or any other appropriate
control, delivery, and/or deployment function control elements. In
alternative embodiments, the user input mechanisms 1060 can
include, but are not limited to, buttons, switches, dials, sliding
elements, or other appropriate mechanical or electrical input
elements. In one example embodiment, the user input mechanism 1060
is a delivery system release mechanism adapted to allow the
delivery system 1000 to be unlocked and disengaged from a cannula
or other working channel. Again, any other appropriate user element
on the delivery system 1000 and/or cannula can be used to release
the delivery system 1000 from the cannula upon completion of the
stent deployment. In a further alternative embodiment, there are no
additional user input mechanisms 1060.
[0164] A method of using the delivery system 1000, in accordance
with one embodiment of the invention, can be seen in FIGS. 11A to
11D. This embodiment includes first inserting the delivery system
1000 into the cannula and locking it in position in a predetermined
set orientation. FIG. 11A shows the delivery system 1000 in its
initial configuration after insertion into a cannula (not shown).
The rotating user control mechanism 1040 on the handle 1010 of the
delivery system 1000 can then be rotated, resulting in the outer
sheath of the elongate shaft being retracted while the inner and
outer shafts are moved forward to compensate for any foreshortening
of the stent during retraction of the sheath, as described above.
FIG. 11B shows the delivery system 1000 after rotation of the
rotating user control mechanism 1000.
[0165] Once the sheath has been retracted, the top cap 1030 of the
handle 1010 can be removed, and a syringe or other cement
deployment device can be attached to a luer lock 1070 (or other
appropriate connection means) at the proximal end of the handle
1010. FIG. 11C shows the handle 1010 with a top cap 1030 removed.
Cement can then be injected through the delivery system 1000 and
into the stent. Once the required amount of cement has been
delivered into the stent, the syringe can be removed.
[0166] The stent release buttons 1050 can then be depressed and
slid towards the proximal end of the handle 1010 (i.e. away from
the elongate shaft 1020) to release the stent from the elongate
shaft 1020. FIG. 11D shows the delivery system 1000 with the stent
release buttons 1050 depressed and slid towards the proximal end of
the handle 1010 to release the stent. The delivery system 1000 can
then be safely removed by activating a delivery system release
button, or other appropriate mechanism, to disengage the delivery
system 1000 from the locking mechanism on the cannula, and removing
the delivery system 1000 from the cannula while leaving the
disengaged stent within the vertebral body.
[0167] In one embodiment of the invention, a distal end of an
elongate shaft can include a preformed curvature. The elongate
shaft can include, but is not limited to, an inner shaft, an outer
shaft, a tubular sheath, a flexible guidewire, and an internal
polymer extrusion. The elongate shaft, or a portion thereof, can be
constructed from a metal including, but not limited to, nitinol,
steel, aluminum, or any other appropriate material such as, but not
limited to, a plastic. The distal end of the elongate shaft can
also include a slotted arrangement allowing the distal end of the
elongate shaft to curve and/or preferentially buckle in a specified
direction. This curving of the distal end of the elongate shaft can
be controlled by a curvature control mechanism located, for
example, within the handle of the delivery system. In an
alternative embodiment, the elongate shaft can preferentially
buckle in response to a force imposed on the distal end of the
elongate shaft by the surrounding bone and/or tissue within the
vertebral body. Example elongate shafts with preformed and
controlled curvature and/or preferential buckling are described in
the related U.S. patent application Docket No. SOT-004, entitled
"Devices and Methods for Vertebrostenting," and filed of even date
herewith, and U.S. application Ser. No. 11/091,232, the disclosures
of which are being incorporated herein by reference in their
entirety.
[0168] In one embodiment of the invention, a stent for use with the
apparatus and methods described herein can include an attachment
mechanism at a distal end thereof (i.e. at the end of the stent
remote from the elongate shaft). This attachment mechanism can
releasably attach to one or more elongate elements extending
through the interior of the elongate shaft.
[0169] In operation of one embodiment, the elongate element
extending through the elongate shaft and attaching to the distal
end of the stent can be used to hold the stent in a collapsed
configuration prior to deployment in place of, or in addition to, a
sheath. When the stent is ready to be deployed, the attached
elongate element can be used to pull the distal end of the stent
rearwards towards its proximate end (i.e. the end of the stent
releasably attached to the distal end of the elongate shaft) in
order to assist in expanding or to forcibly expand the stent. This
may be advantageous in embodiments of the invention using a stiffer
and/or thicker stent, that may benefit from additional external
forces to assist in its expansion or to provide positive forces on
the walls of a cavity in which it is inserted. For example, a
stiffer stent, with a more substantive mesh structure, can be used
to provide a jacking force to expand the size of a cavity and/or
jack or push two walls of a collapsed vertebral body apart. In this
embodiment, the self-expanding nature of the stent may not provide
sufficient force in and of itself to provide a jacking force of
desired magnitude. The additional force needed to allow the stent
to jack the walls apart can be provided by the pulling force
applied to the distal end of the stent by the releasably attached
elongate element. After the stent has been expanded, the elongate
element can be released from the stent and removed through the
elongate shaft.
[0170] The elongate element releasably attached to the distal end
of the stent can also be advantageous in embodiments where a cavity
has not been reamed out in the vertebral body, or other structure,
but rather only a drill hole has been created in the vertebral body
sufficient in size to receive the stent in a collapsed
configuration. In this embodiment, the elongate element can be used
to pull on the distal end of the stent and assist in expanding it
into the body structure surrounding the drill hole. This method may
be useful, for example, in the treatment of seriously degraded
vertebral bodies, where the stent can be expanded into the
surrounding degraded bony structure with nominal additional
force.
[0171] An example stent deployment method including a stent with an
attachment mechanism at its distal end can be seen in FIGS. 12A to
12D. In this embodiment, a stent 1205 is releasably attached at its
proximal end 1210 to an elongate shaft 1215 including an inner
shaft 1220 and an outer shaft 1225. The means of releasably
attaching the stent 1205 to the elongate shaft can include any of
the mechanisms and methods described herein.
[0172] A ferrule 1230 is placed against the interior wall of the
distal end 1235 of the stent 1205, with a locking ring 1240 holding
the ferrule 1230 in place against the wall of the distal end 1235
of the stent 1205, for example by a radial interference fit. The
ferrule includes a hollow proximate end 1245 with two slots 1250
formed in the walls thereof. The slots 1250 are adapted to
releasably engage an elongate attachment element 1255 with a pair
of tangs 1260 at a distal end thereof. The tangs 1260 are bent in
towards the central axis 1275 of the elongate attachment element
1255 such that the tips 1265 of the tangs 1260 can be extended into
the hollow proximate end 1245 of the ferrule 1230. In an
alternative embodiment, a greater or lesser number of slots 1250
and corresponding tangs 1260 can be used.
[0173] Once the tips 1265 of the tangs 1260 have been extended into
the hollow proximate end 1245 of the ferrule 1230, an inner rod
1270 is extended through the elongate attachment element 1255 to
abut against the inner walls of the tangs 1260. By pushing the
inner rod 1270 forward towards the distal end 1235 of the stent
1205, the inner rod 1270 pushes the ends of the tangs 1260 outwards
from the central axis 1275 of the elongate attachment element 1255
such that the tips 1265 are forced into the slots 1250 in the
ferrule 1230. As a result, the elongate attachment element 1255
becomes releasably coupled to the ferrule 1230 and can therefore
provide a pulling force to the distal end 1235 of the stent
1205.
[0174] In operation, the elongate attachment element 1255 is
coupled to the ferrule 1230 prior to deploying the stent 1205 in
the vertebral body. To facilitate insertion of the stent 1205
through the cannula, and into the vertebral body, the elongate
attachment element 1255 is pushed forwards against the distal end
1235 of the stent 1205 to force the stent 1205 into a collapsed
configuration, as shown in FIG. 12A. In one embodiment a sheath can
be extended over the stent 1205 to hold the stent 1205 in a
collapsed configuration, with the sheath being retracted once the
stent 1205 is in position within the vertebral body, as described
above. In an alternative embodiment, no sheath is required, with
the elongate attachment element 1255 providing sufficient force to
maintain the stent 1205 in a collapsed configuration.
[0175] Once the stent 1205 has been positioned correctly within the
vertebral body, the elongate attachment element 1255 can be pulled
back by a set amount, dependent upon the size and shape of the
stent 1205, thus pulling on the distal end 1235 of the stent 1205
and forcing it to expand to its deployed configuration, as shown in
FIG. 12B. Advantageously, as the distal end 1235 of the stent 1205
is pulled back, the proximal end 1210 of the stent can be advanced
or pushed forward, in order to expand the stent 1205 while leaving
a midpoint of the stent 1205 in essentially a fixed position in the
cavity in the vertebral body. This coordinated action of retracting
the distal end 1235 while advancing the proximal end 1210 can be
accomplished using the types of mechanisms described above located
in the handle.
[0176] After the stent 1205 has been positioned in its deployed
configuration, the inner rod 1270 can be pulled out from the
elongate attachment element 1255, as shown in FIG. 12C. As the
inner rod 1270 is pulled out, the tangs 1260 collapse back into
their initial configuration (i.e. bent in towards the central axis
1275 of the elongate attachment element 1255). This in turn removes
the tips 1265 of the tangs 1260 from the slots 1250 of the ferrule
1230, thus disengaging the elongate attachment element 1255 from
the ferrule 1230. The elongate attachment element 1255 can then be
pulled out from the ferrule, leaving the distal end 1235 of the
stent 1205 free.
[0177] In one embodiment, the elongate attachment element 1255 is a
hollow needle adapted to inject cement into the stent 1205. In
operation, once the inner rod 1270 has been removed and the
elongate attachment element 1255 detached from the ferrule 1230,
cement can be injected through the elongate attachment element 1255
and into the interior of the stent 1205 to fill the stent 1205, as
shown in FIG. 12D. After the stent 1205 has been filled with cement
to the volume required, the elongate attachment element 1255 can be
removed and the stent 1205 detached from the elongate shaft. In an
alternative embodiment, the elongate attachment element 1255 can
simply be removed from the elongate shaft 1215 after deployment of
the stent 1205, with cement, or any other appropriate filler
material, being injected thereafter into the stent 1205 directly
through the inner shaft 1220 of the elongate shaft 1215, or through
a separate cement injection element.
[0178] The elongate attachment element 1255, elongate shaft 1215,
ferrule 1230, locking ring 1240, and inner rod 1270 can be
constructed from materials including, but not limited to, a metal
(e.g. nitinol, steel, aluminum, or any other appropriate metal), a
plastic, and/or a composite material.
[0179] In an alternative embodiment, the ferrule 1230 can be
attached to the distal end 1235 of the stent 1205 by any other
appropriate method, such as, but not limited to, being glued to,
welded to, or otherwise attached to the stent 1205. In further
alternative embodiments, the elongate attachment element 1255 can
be releasably attached to the ferrule by any appropriate
mechanical, electrical, thermal, or magnetic connection means.
[0180] In alternative embodiments of the invention, any appropriate
material, or combination of materials, may be used for the
components of the delivery system. Appropriate materials include,
but are not limited to, stainless steel, aluminum, plastics,
textiles (for the sheath), composite materials, or any combination
thereof. The delivery system may be configured with all, or only
some of, the components described herein, depending upon the
specific requirements of the system.
[0181] The delivery system may be configured to deliver cement,
cement analogue, or other appropriate filler material, to any
appropriate stent, bag, or other fillable device. In one
embodiment, the stent need not have holes for the directed exit of
the cement into the vertebral body. The delivery system may be
configured to delivery a stent, or other device, to a cavity in any
bony structure, and not just a vertebral body. Additionally, any
appropriately shaped cavity may be treated with the above-mentioned
delivery system and stents.
[0182] It should be understood that alternative embodiments, and/or
materials used in the construction of embodiments, or alternative
embodiments, are applicable to all other embodiments described
herein.
[0183] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The foregoing embodiments, therefore, are to be considered
in all respects illustrative rather than limiting the invention
described herein. Scope of the invention is thus indicated by the
appended claims, rather than by the foregoing description, and all
changes that come within the meaning and range of equivalency of
the claims are intended to be embraced therein.
* * * * *